This invention relates generally to computer systems, and more particularly to computer systems utilizing graphical user interfaces.
Graphical user interfaces or GUI are becoming increasingly popular with computer users. It is generally accepted that computers having graphical user interfaces are easier to use, and that it is quicker to learn an application program in a GUI environment than in a non-GUI environment.
A relatively new type of computer which is well suited for graphical user environments is the pen-based or pen-aware computer system, hereinafter generically referred to as a "pen computer system," "pen computer," or the like. A pen-based computer system is typically a small, hand-held computer where the primary method for inputting data includes a "pen" or stylus. A pen-aware computer system is one which has been modified to accept pen inputs in addition to traditional input methods.
A pen computer system is often housed in a relatively flat enclosure, and has a dual-function display assembly which serves as both an input device and an output device. When operating as an input device, the display assembly senses the position of the tip of a stylus on the viewing screen and provides this positional information to the computer's central processing unit (CPU). Some display assemblies can also sense the pressure of the stylus on the screen to provide further information to the CPU. When operating as an output device, the display assembly presents computer-generated images on the screen.
Typically, graphical images can be input into the pen computer systems by merely moving the stylus across the surface of the screen, i.e. making a "stroke" on the screen. A stroke can be defined as the engagement of the screen with a stylus, the movement of the stylus across the screen (if any), and its subsequent disengagement from the screen. As the CPU senses the position and movement of the stylus, it can generate a corresponding image on the screen to create the illusion that the stylus is drawing the image directly upon the screen, i.e., that the stylus is "inking" an image on the screen. With suitable recognition software, text and numeric information can also be entered into the pen-based computer system in a similar fashion. Methods for recognizing the meaning of "ink" are well known to those skilled in the art.
Pen computer systems tend to discourage the use of a keyboard as an input device. Most of the software written for pen computers is designed to function well with pen strokes and by "tapping" the stylus against the computer screen in defined areas. A "tap" is a stroke which does not move substantially across the screen. In addition, a primary feature of many pen computer systems is their portability, which a keyboard, if included with the pen system, would seriously degrade.
In some instances, however, the need arises on a pen-based computer for data entry in a keyboard-like fashion. For example, the pen-based computer might be running a non-pen aware program that normally accepts characters from a keyboard. Also, in some cases, the only way to enter data efficiently might be to use a keyboard-like input device.
In particular, a need might arise on a pen computer to enter command or character that is normally or most efficiently executed with keystrokes on a keyboard-based system. In some pen computer systems, such keyboard-like entry of commands can be accomplished using a keyboard image displayed on the screen of the pen computer. The keyboard image resembles a standard keyboard, and keys are selected using a stylus. Most keyboard commands and characters can be entered in this fashion. Another alternative is to provide a recognition window for inputting handwritten data which is then recognized and sent to an application program as if it were typed from a keyboard. A problem with all such input approaches is that they occupy valuable screen space, which is often very limited on pen computer systems.
The efficient use of the available display screen space for observation of images and windows containing images, while particularly pronounced for pen computer systems, is common to all computer systems which display information or images to the user. No matter how large a particular display may be, a particular user will be tempted to attempt to display more information on the screen than can effectively be handled.
Images or information presented on a display screen are typically presented as opaque images, i.e., images "behind" a displayed image are obscured. This is the case with display windows which are layered on a particular screen, with the uppermost window image partially or completely blocking the view of the lower windows. For two windows to be capable of interaction, it is preferable that the user be able to observe both images at the same time, or at close to the same time.